Tracking flowpaths in a complex karst system through tracer test and hydrogeochemical monitoring: Implications for groundwater protection (Gran Sasso, Italy)

Groundwater in karst aquifers is frequently tapped for drinking purposes, due to frequent huge
volumes of resources. Unfortunately, vulnerability of these aquifers can be high, due to possible
fast transfer of recharge water on springs by the karst network. On Gran Sasso Mountain regional
aquifer, several springs are subjected to drinking withdrawal and an updated evaluation of their
potential is now a fundamental issue to be considered, facing climate change effects, which reflect
on variation of discharge regimen and values. To distinguish between different contribution of
spring recharge, a tracer test has been carried out on the Vitella d’Oro spring, fed both by the
regional aquifer and by a local system exposed to karst features developed in the Rigopiano
Conglomerates formation. Thanks to hydrogeological, hydrogeochemical and isotopic data, a
conceptual model of spring recharge has been proposed and subsequently validated by the tracer
test results. All information confirms the superimposition on the regional base flow, by a relevant
contribution of the karst network, influencing the spring discharge in recharge periods. ... mehrIn detail,
a fast flow component is responsible for discharge peaks and frequently of turbidity events,
having a mean velocity ranging from 30 to 70 m/h in the aquifer. Besides of this fast flow, an
additional aliquot of the recharge is due to the same local aquifer, but slower flow clearly
identifiable by hydrochemistry and isotopic data. Thanks to these findings, a renewed manage-
ment of the spring has been suggested, considering the different degrees of aquifer vulnerability
(turbidity occurrence) directly related to the discharge regimen.